The present invention relates generally to hydraulic pumps. More particularly, the present invention relates to a cartridge-style vane pump that can be assembled and tested separate and apart from its housing.
The use of hydraulic pumps, such as power steering pumps, is well known in the automotive industry. Conventional hydraulic pumps, such as those used in power steering systems, are positive displacement pumps.
These positive displacement pumps are typically driven by a drive shaft which is driven by the vehicle engine through an accessory drive system or by the shaft of an electric motor in electrically powered systems. These motor or engine shafts are known to fluctuations that are transmitted to the hydraulic pump by direct coupling of the drive shaft to the hydraulic pump. Motor drive shafts are known to have fluctuations that are transmitted to the hydraulic pump or gear pump by direct coupling of the drive shaft to the hydraulic pump. Current motor drive shafts extend into the pump housing, creating pressure pulsations that can cause the motor to become misaligned with respect to the drive shaft and the pump reservoir.
To eliminate these misalignment problems, current pump designs, including the pump associated pump reservoir and shaft, are typically fully assembled and then transported as a single unit. A typical pump design is assembled by first placing the lower plate of the pump and the pump rotor assembly over the motor drive shaft. Thereafter, a retaining ring is used to lock the rotor onto the drive shaft. Alignment pins are then placed into the lower plate for alignment of the lower plate with respect to the drive shaft over which it was previously placed. The upper plate and the pump cover are then fit onto the alignment pins to align the upper plate and pump cover with respect to the lower plate. An o-ring seal is then placed both on the outside and on the inside of the lower plate and on the pump cover. The assembly is then placed into a pump housing for which it was designed. This completely assembled unitary pump unit is relatively large and expensive. Moreover, because the pump is secured to the pump cover any misalignment of any portion of the pump can cause fluctuations in flow or pressure.
It would therefore be desirable to provide a pump for use in a power steering system that is smaller and less expensive. Further, it would be desirable to have a cartridge-type pump that can be utilized in a variety of different pump reservoirs or housings.
It is therefore an object of the present invention to provide a cartridge-style vane pump for use in a vehicle power steering system. It is a further object of the present invention to provide a cartridge-style pump that is less expensive to manufacture and assemble than prior pumps and is more precise.
In accordance with the objects of the present invention, a cartridge-style vane pump for use in a power steering system is provided. The pump includes an upper plate, a lower plate, and a cam plate disposed between the upper plate and the lower plate. The cam plate has a rotor disposed in a bore formed therein. The rotor is preferably a vaned rotor that pumps fluid from a fluid reservoir to a power steering gear. A plurality of alignment pins are press fit into the lower plate of the pump and pass through passages in the cam plate and the upper plate to align the plates and hold them together. A plurality of retaining clips are secured on a respective one of the plurality of alignment pins in order to firmly secure the plates together to form the cartridge-style vane pump. This configuration allows the cartridge-style vane pump to be built and tested separate from an associated pump housing into which the pump is intended to be fit.
Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.